601.4 Contamination prevention.
MC § 601.4
Exhaust ducts under positive pressure, chimneys and vents shall not extend into or pass through ducts or plenums. Exceptions: 1. Exhaust systems conveying Class 1 or Class 2 air in accordance with ASHRAE 62.1, located in return air plenums and that have exhaust duct joints, seams and connections that comply with Section 603.9 without taking any exceptions. Such exhaust system and plenum shall be subject to special inspection in accordance with Section 1705.39 of the New York City Building Code and shall be subject to periodic inspection in accordance with Section 602.6 of this code.
2.This section shall not apply to chimneys and vents for appliances with a heat input not greater than 350,000 Btu/hr (103 kW) that pass through plenums provided that such venting systems are subject to special inspection in accordance with Section 1705.39 of the New York City Building Code and shall be subject to periodic inspection in accordance with Section 602.6 of this code and comply with one of the following requirements: 2.1. The venting system shall be listed for positive pressure applications and shall be sealed in accordance with the vent manufacturer's instructions. 2.2. The venting system shall be installed such that fittings and joints between sections are not installed in the above ceiling space. 2.3. The venting system shall be installed in a conduit or enclosure with sealed joints separating the interior of the conduit or enclosure from the ceiling space.
